README.md

ngrx-dynamic-view-model

Development server

Run ng serve for a dev server. Navigate to http://localhost:4200/. The app will automatically reload if you change any of the source files.

Concept

One of the core beliefs of my architecture team at work is that most of the common functionality that builds out a view can be abstracted away, so that data fetching is no longer a concern for developers doing feature work. This project acts as a PoC to prove out that concept, using @ngrx/store to maintain and distribute application state for each view. It will likely serve as an example for how we will continue to work on our existing data resolution pipeline.

Key features

First and foremost, the data resolution model identified here makes use of service abstraction to fetch data. While the DataService in this application maintains a list of hard-coded JSON file paths, in a real world application this would map dependency data commands (e.g. get-bands) to backend services by fetching an API configuration mapping from a middleware reverse proxy. That allows API endpoints to remain anonymous to the front-end code, while still creating a functional REST relationship between the front-end and backend services. Totally freaking baller.

Each route defines the data it needs resolved, and in declaring its actions as values of data keys, it creates a dictionary object for the ModelResolve to populate. For example, in the band/:id/song/:songId route, we have the following definition:

{
band: 'get-band',
song: 'get-song'
}

The ModelResolve will re-map those values into an object containing the same keys, with the values replaced as Observables that return data from the backend. This is simulated using hard-coded JSON files served over HTTP.

Since each view (often referred to as Smart Components) receives its data from the Store and passes it down through the component tree, we can extract the boilerplate code that makes that work into a base class that each view can inherit from. Hence the creation of the BaseView. The BaseView handles subscribing to the Store in the ngOnInit hook, as well as un-subscribing as part of the ngOnDestroy lifecycle hook. Devs can add functionality to the ngOnInit or ngOnDestroy hook using the baseViewHooks property.

By default, data is automatically removed from the Store or overwritten when a view is destroyed. This is also handled by the BaseView in its ngOnDestroy hook. This can be prevented by passing in an object to the super call when extending the BaseView. The goal is to prevent the state from getting too bloated as the user navigates through the app.

Alternatively, a dev could choose not to extend the BaseView when creating a view. This would leave the subscribing, un-subscribing, and maintenance of the Store entirely up to them. So long as dependencies are listed within a route declaration, and the ModelResolve is set on a route.data property, fetched data will automatically be added to the Store when a route is loaded.

To that end, in theory, if a root view contained all of the data necessary to load an application, a dev could load it all into the Store at startup, and then ensure that it's maintained throughout the use of the app. That's a bit extreme, but you get the idea.